1. Field of the Invention
The present invention relates to a stopper cylinder which makes it possible to stop a conveyed workpiece and position it at a predetermined position by the aid of a lock mechanism.
2. Description of the Related Art
The stopper cylinder has been hitherto used, for example, in order that a workpiece, which is conveyed on a conveyer line provided with a plurality of roller conveyers or the like in an aligned manner, is stopped at a predetermined position.
That is, the stopper cylinder comprises a piston rod which is movable frontward and rearward in accordance with an energized action thereof, and a lever which is engaged with a forward end of the piston rod. The lever is allowed to protrude by a predetermined length upwardly from the conveyance plane of the conveyer line through the gap between the adjacent roller conveyers so that a conveyed object abuts against guide rollers provided on the lever. Thus, the stopper cylinder functions as a stopper for stopping the conveyed object.
The stopper cylinder concerning the conventional technique is disclosed, for example, in Japanese Laid-Open Utility Model Publication Nos. 64-39318 and 64-39319, and Japanese Utility Model Publication No. 4-30183.
Such a stopper cylinder concerning the conventional technique contains a shock absorber which functions to relieve the shock upon abutment of the lever against a workpiece. The stopper cylinder further comprises a lock mechanism for preventing the workpiece from being pushed and returned in a direction opposite to the conveyance direction by the buffering force of the shock absorber when the workpiece is stopped at a predetermined position, and avoiding restoration of the lever to smoothly ensure a stopped state of the workpiece.
However, the stopper cylinder relevant to the conventional technique as described above involves the following inconvenience concerning the locked state in which the lever protrudes upwardly from the conveyance plane for the workpiece to make it possible to stop the workpiece which is conveyed in a predetermined certain direction. That is, if the workpiece is conveyed in a direction opposite to the predetermined conveyance direction, the lever is not released from the locked state even when the workpiece abuts against the lever. For this reason, it is impossible to convey the workpiece in the opposite direction.
In other words, the following inconvenience arises. When an adjusting operation is performed before the conveyer line is automated by installing the plurality of roller conveyers to construct the conveyer line, the worker occasionally wishes to manually move the workpiece in the direction opposite to the previously established workpiece conveyance direction. In such a case, even when the workpiece, which is moved in the direction opposite to the predetermined conveyance direction, abuts against the lever of the stopper cylinder, the lever is not released from the locked state. Therefore, it is impossible for the worker to move the workpiece in the direction opposite to the conveyance direction.